Satellites with reconfigurable payloads provide desirable on-orbit mission flexibility. A reconfigurable payload allows a satellite to change the shape and location of its beams in order to change earth coverage regions. These changes may be necessary in order to compensate for spacecraft yaw steering, to back up or replace another satellite in-orbit, or as a result of changing market demands or customer requirements.
One approach to providing a reconfigurable payload involves using a Gregorian reflector antenna with an elliptical sub-reflector in order to produce a very broad elliptical beam. By rotating the elliptical sub-reflector, the far-field beam can be rotated to compensate for the yaw rotation of the satellite. This approach suffers from reliability problems because the reconfiguration is mechanical. Moreover, the gain of such an antenna is insufficient for many applications.
Another approach to providing a reconfigurable payload uses phased array optics to illuminate a reflector. In this approach, several hundred optical elements are used to provide the required phase delay between elements. Because of the large number of elements, this approach suffers from increased mass and expense. Moreover, this approach is unsuitable for handling large power loads due to the fact that the large number of amplifiers required can not be accommodated on a spacecraft. Other limitations include the difficulty of power dissipation and very high cost.
Yet another approach uses a system in which a feed array is located out of the focal plane of a parabolic reflector to de-focus the beam. This approach provides limited or no beam reconfiguration. Further, because the basic reflector geometry is de-optimized, the system suffers from increased scan losses, inferior cross-polar performance, mutual coupling effects and the like. Moreover, the number of optical and other elements required is still undesirably large, and the system requires complex input and output hybrid matrices.
Accordingly, there is a need for a flexible, reconfigurable payload with less complexity, more beam configurability, better reliability, and higher performance. The present invention satisfies these needs, and provides other benefits as well.